1. Field of the Invention
The present invention relates to a peer to peer (P2P) content delivery system which includes a plurality of node devices which are connected with each other via a network and, especially, relates to a technical field of an information delivery system, delivery request program, transfer program, delivery program, and the like in which content data which is to be delivered from one node device to the other is distributed and saved in a plurality of node devices.
2. Discussion of the Related Art
In this kind of content delivery system, each of node devices has a list in which location information regarding content data distributed to and saved in a plurality of node devices is described (for example, information which enables to specify an IP address or the like of a node device which saves the content data by designating auxiliary information such as a title of the content data: Hereinafter referred to as index information) and on the basis of index information described in the list, it becomes possible to download content data which a user wants. Such a list is common information to be used commonly among a plurality of node devices and generally is managed by a management server which manages all the content data saved on a content delivery system so that the list is delivered from the management server to each node device.
For example, in the Nonpatent Document 1, as a method which does not use a management server, a technique using a distributed hash table (DHT) has been disclosed. In this system, a request node device which requests delivery of content inquires location of a node device, which saves content information, to a management server which manages content information to access the node device.
Nonpatent Document 1: “Lightweight Load Balancing for Distributed Hash Tables”. Technical Report of the Institute of Electronics, Information, and Communication Engineers.